Telautograph receiver



Nov. 9, 1937.

A. J. WOH LG EM UTH TELAUTOGRAPH RECEIVER Filed Feb. 14, 1935 will? JIM-4| m Fiji;

INVENTOR} Patented Nov. 9, 1937 UNITED STATES TELAUTOGRAPH RECEIVER Adolph J. Wohlgemnth Brooklyn, N. Y., assig'nor to Thomas Electric Company, West New York,

Application February 14, 1935, Serial No. 6,504

4Claims.

The object of this invention is to provide means for graphical representation over lines of considerable length.

Another object of this invention is to provide .6 means for using a large and varying number of telautographic instruments in multiple over two small gauge transmission lines.

The further object of this invention is to provide a sensitive penlifter circuit that can be used 10 over long lines in a large multiplicity.

Another object of this invention is to enable alternating or direct current to be applied to the rheostats of the transmitter, and to enable alternating current to be used at one end with 15 direct current at the other end.

Still another object is to enable the receiver to operate with substantially no current flowing from the transmitter to the receiver.

A further object is to enable any amount of 20 current desired, from substantially zero to the limit of the line, to flow from the transmitter to the receiver.

A still further object is to accomplish the pur pose with the simplest equipment and in the most 5 economical manner.

Referring to the drawing:

Figure 1 is a circuit diagram of a telautograph transmitter illustrating the principle of operation.

30 Figure 2 is the circuit diagram, illustrating a type of telautograph receiver to show the principle of operation.

Figure 3 is the circuit diagram of the telautograph receiver of this invention.

In Figure 1 and Figure 2 there is shown for the purpose of illustration a circuit diagram outlining one of the various types of telautograph systems, the method of operation of which is as follows:

40 An operating stylus I is connected to a linkage system 2 and 3 having two degrees of freedom. The movement of the linkage arms 2 and 3 controls two rheostats 4 and 5, one for each degree of freedom, which in turn vary the direct our- 45 rent potentials applied to the two separate circuits L1 and L2.

The apparatus for touching the pen to the paper and lifting it off is controlled by the pressure of the stylus on platen 6. In writing, this 50 pressure disconnects a short circuit across an alternating current channel from source I which is superimposed on the two direct current channels from lines L1 and L2 by the capacitive coupling of condensers 8 and 9. To prevent this 55 alternating current from short circuiting through the rheostats I and 5, the chokes I and II are connected in lines L1 and L2 of high inductance but low resistance. The direct current for this system is supplied by battery I2 through switch I3. The positive terminal of the battery I2 is grounded.

At the receiving end, shown in Figure 2, the direct currents operate two relays I4 and I5 and actuate two solenoids I6 and I1 and retdm to the battery by the earth connection I8. When relay I4 is energized, the contact on it closes the circuit for the battery I! to energize the field coil 20. This energizes the field coil 20 very strongly, making it a large magnet of which one pole is a North pole and the other a South pole. The solenoids I6 and I I are so wound that, using the law that like poles repel and unlike poles attract, they are moved to a position of equilibrium against a spiral spring attached to shafts 28 and 29. The rheostats l and 5 are so shaped that the solenoids move the rotatable segments 30 and 3| until the linkage 2| and 22 assume the same position as the linkage. 2 and 3. This causes the pen 23 to'execute a motion reproducing that of the sending stylus I.

The paper shifting mechanism 24 is operated by the contacts on relay I l which in turn is operated from the transmitter by switch I3. The mechanism for lifting the pen is actuated by the alternating current coming over the lines L1 and La from the source I. At the receiver, it is given a low impedance path thru condenser 25 and alternating current relay 26, and a high impedance path through the solenoids I6 and IT on account of the high inductance of the windings of relays I4 and I5. 'In that way, the alternating current is largely confined to the path through condenser 25 and alternating current relay 26. It was noted that when the stylus I is raised, there is a short circuit at platen 6 and no alternating current flows. When no alternating current flows, the armature of relay 26 falls back, closing the circuit from battery I9 through the contacts of relay I4, through the back contacts of i'elay 26, thru the penlifter mechanism shown as 21, back to the battery IS. The penlifter mechanism 21 thus energized, lifts the pen oil of "the paper.

However, when the stylus I is pressed on platen 6, the circuit at platen 6 is opened and alternating current flows from source I through the eondensers 8 and 9 over lines L1 and L2 to condenser 25 and relay 26. When the relay 26 is thus energized the circuit is opened and the armature of the penlifter mechanism 21 falls back allowing the pen to touch the paper.

Referring to Figure 3 considering that the same voltages are on lines L1 and La as are illustrated by Figure 1, the direct current voltage is applied to the grids 32 and 33 of vacuum tubes 34 and 35. The cathodes 33 and 31 are connected together to ground 33. The voltage from battery 39 is applied to the plates 43 and 4| through the solenoids l3 and I1 and the relays l4 and I5. Since the voltages as shown are negative to ground on the lines L1 and In and the voltage on the plates 40 and 4| are positive to ground, and the cathodes 36 and 31 are grounded, the voltage on the grid controls the'plate current and can reduce the plate current to zero by increasing the negative grid voltage to the cut-off voltage of the tube and the plate current will be maximum when the negative grid voltage is zero. Thus the current through the solenoids i and I1 can be varied from zero to maximum by means of the rheostats 4 and 5.. However, the variation of resistance in the rheostat will not be the same as for the direct connection of the solenoids l4 and H as shown in Figure 2. It will be noted that the potential of the grid is kept negative at all times with respect to the cathode in order that the grids 32 and 33 shall not draw current. By placing resistances from each line L1 and In to ground 33 current can be drawn over the lines without having the grids 32 and 33 use current and so still use the static characteristics oi the tube.

The operation of paper shifter 24 and the iield 23 from battery 33 through the contacts oi relay 14 through the paper shifter 24 and the held 20 to ground, and the other side of battery 39, is the same as described previously.

However when the current reaches a certain minimum value, the armature of relay I5 falls back before the armature of relay |4 does, and connects the negative bias from battery 42 through the back contact of relay I 5 and through resistances 43 and 44 to lines L1 and L1 respectively, biasing them to cut-oil, so that switch l3 may be opened. If that were not done, the grids would have no negative bias on them and the maximum plate current for the circuit would flow.

If the switch 3 is closed again, a certain current will flow over the' line from battery 42 through resistors 43 and 44, through lines L1 and L; through the rheostats 4 and 5 to ground at battery l2. The current will be very small as it will be due only to the difierence in potential between battery 42 and the potential of the point on rheostats 4 and 5 corresponding to the position of the stylus. However resistors 43 and 44 are of the order of three to six megohms, so that even a small current causes a comparatively large voltage drop across them. As the stylus I is moved from the position of minimum current, the potential difierence between the point on the rheostats and battery 42 will be increased causing more current to flow and hence a larger drop across resistors 43 and 44 until the voltages at grids 32 and 33 are below the cut-off voltage. Current will then flow in the plate circuits picking up relay 5 to remove the bias voltage and relay l4 to shift the paper and energize the field.

when the stylus is depressed and an alternating potential is applied to the lines L1 and L: as previously described, the voltage comes in on lines L1 and L: to grids 32 and 33, thence to plates 40 and 4| of vacuum tubes 34 and 35. As before, relays i4 and I! prevent the alternating current from flowing through the solenoids l6 and 1. The alternating current then follows the path from plate 40 through condenser 45 and resistances 41 and 5| to the cathode 50 of vacuum tube 52. Then the path is to the diode plate 49, the resistance 48, and the condenser 46 to plate 4|.

The action of the diode plate is to rectify the alternating current. This causes a potential to be set up across resistance 5| with point 52 to be at a negative potential with respect to the cathode 50. That negative potential is applied to the grid 55 of a triode in the same tube 62 through grid leak 54 and condenser 53. The value of resistance 5| is so chosen that the grid 55 is biased to cut-oil when the alternating current is flowing. The plate 56 is connected to penlii'ter 21 and through that and through the contacts of relay l4 to the battery 39.

From the foregoing it can be seen that when no alternating current is applied, the plate current will be maximum since there will be no grid bias thus energizing the penlifter 21 and lifting the pen of! the paper. However, when the stylus is pressed on platen 6, the short circuit is removed and the alternating current from source 1 is applied to the lines Li and L2. This is impressed into the plate circuits 40 and 4| of vacuum tubes 34 and 35 and thence through condensers 45 and 45 and resistances 41, 43 and 5| to the diode unit of vacuum tube 62. The rectifying action of the diode sets up a negative bias across resistance 5| which at 52 is applied to the grid 55 to cut-off the plate current from penlifter 21 allowing the pen to press on the paper.

There are also batteries 60 and 5| to supply current for the heaters 51, 58, and 59.

If battery l2, in thetransmitter, is replaced by an alternating current generator of a frequency widely difierent from the frequency of alternating current generator 1, the receiver in Figure 3 will operate as described, provided a negative bias is connected to grids 32 and 33 of vacuum tubes 34 and 35.

While the foregoing is a description and explanation of the particular circuit illustrated, I am aware that those skilled in the art will see numerous other arrangements that can'be made without departing from the spirit of the invention.

What I therefore claim is:

1. A telautographic' communication system comprising a sending station, a source of direct current at the sending station, a pair of lines, a receiving station, vacuum tubes connected to said lines at the receiving station, a pair of relays responsive respectively to different minimum currents controlling the graphic representation means and each connected to the plate of one of said vacuum tubes and a source of auxiliary potential at the receiving station in the circuit controlled by the relay responsive to the higher minimum current, and means for applying said auxiliary potential to the control electrodes of said vacuum tubes on the passage 01' said higher minimum current to cut oil the current in the plate circuits of said vacuum tubes.

2. In a telautographic receiver, a vacuum tube including a control electrode and an output electrode, a communication line, a direct connection from the line to the control electrode, graphic representation means connected to said output electrode, and means for applying an auxiliary negative potential to the control electrode to increase the total negative potential thereon to the cut oil potential of said tube when the current in said output electrode falls below a predeter mined minimum.

3. In a telautographic commimication system, a source of alternating current potential, a pair of operating lines, vacuum tubes connected to each of said pair of lines, graphic representation means in the output circuits of said vacuum tubes, a resistance and rectifier connected in series and the combination connected in shunt of the output circuits of saidvacuum tubes, a thermionic tube having a control electrode and an output electrode, a penlifting mechanism connected to the output electrode of said thermionic tube, and a connection between the control electrode of said thermionic tube and a predetermined point on said resistance to bias said control electrode to cut oil and thus release said pen lifting mechanism when said alternating current potential is applied to the lines.

4. In a telautographic communication system, a source of direct current potential, a source of alternating current potential, a pair of operating lines, a graphic representation device, a circuit including electromagnetic means for operating said device in a plane by said direct current, and a circuit including a rectifier, a condenser, and a biasing resistance connected in series between said operating lines, responsive to said alternating current through the control electrode of a vacuumtube connected to the biasing resistance, the output electrode of said vacuum tube connecting to electromagnetic means for moving said graphic representation device at right angles to said plane.

ADOLPH J. WOHLGEMU'I'H. 

